Archaeal host virus interactions

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Abstract

Viruses are the most abundant biological entity on earth, and virus-host interactions are one of the most important factors shaping microbial populations (Suttle, 2007b). The study of both the cellular and viral members of the domain Archaea is a relatively new field. Thus, the viruses (and their cellular hosts) of Archaea are poorly understood as compared to viruses of Bacteria and Eukarya. This work has sought to expand our understanding of archaeal viruses by two general approaches. The first is by developing and implementing the use of a genetic system for a crenarchaeal virus, Sulfolobus turreted icosahedral virus (STIV), isolated from a hot (82°C) acidic (pH 2.2) pool in Yellowstone National Park, USA. The second approach has been to look at viral communities and their interactions with their cellular hosts in natural environments. We have developed a genetic tool, an infectious clone for STIV, which has allowed for genetic analysis of this virus. A number of viral genes have been knocked out, and their functions investigated using this tool. We have determined that at least three viral genes, A197, B345 and C381, are required for viral replication, while one gene, B116, is not essential. Work continues investigating function for other STIV genes as well as specific interactions with its host, Sulfolobus solfataricus. We have performed total community sequencing (metagenomics) for both the cellular and viral populations of several hot springs in Yellowstone National Park. We have been able to assemble a near full-length putative novel viral genome from one of these sites. We have also performed an in depth analysis of the function of a newly described bacterial and archaeal adaptive immune system (CRISPR/Cas) in a natural environment. This study has provided insights into the function of this immune system in a complex nutrient limited environment, which would not have been observed by studying cultured isolates in a laboratory.